The prior art for making molds or tooling deals for the most part with fabricating, machining, layered deposition forming, molding or casting of tools for a single dedicated purpose. While the tools may be modified or the materials recycled, often this is accomplished only with multiple steps and at considerable expense. Specific instances of quickly reformable molds have been found which rely on beads, sand or other particulate materials being blown or poured into a container with at least one flexible or elastically extensible surface. An article is pushed against or surrounded by the flexible surface and the contained particulate material, and then a vacuum is pulled on the container to remove air so that ambient air pressure consolidates the beads or particles and holds the flexible surface against them in the shape of the article. Likewise, numerous instances have been found of cushions, pads or seats which rely on introducing or vacuuming air from a bead-filled, flexible or stretchable sealed envelope, while other instances have been found of reformable shapes comprising flexible envelopes which contain mixtures of beads or microspheres combined with binding yet flowable lubricants or highly viscous materials. Some of these shapes have been made temperature responsive, so that heat would soften them and cooling would harden them.
U.S. Pat. No. 5,348,070 (Fischer et al.) is titled xe2x80x9cProcess for the Compression of Molding Sand for Casting Molds,xe2x80x9d and discloses a method for closely packing sand into a mold through a process of fluidizing it within the mold by a surge of compressed air through the sand and then compressing it by mechanical pressing. The technique requires a pressure rise and a pressure reduction gradient in the fluidizing process and requires initiating the mechanical pressing operation during the controlled pressure reduction. This multi-step process allows the sand grains to be jostled into any voids which could form as a result of particles being allowed to statically press on one another.
U.S. Pat. No. 5,957,189 (Uzaki et al.) describes an xe2x80x9capparatus and method for sequentially feeding quantities of sand into a mold space and subjecting the space to evacuation and then pressure increase after each feed.xe2x80x9d The process differs from Fischer in that layers of sand are placed in the mold and consolidated by evacuation of air followed by rapid pressurization or pulse of compressed air, thus avoiding the need for a mechanical tool to press the sand. As with Fischer the pressure uses a considerable amount of compressed air and also requires a vacuum source.
U.S. Pat. No. 5,971,742 (McCollum) is titled xe2x80x9cApparatus for Molding Composite Articlesxe2x80x9d and describes liquid-supported thin-shell molds. These rapid molds utilize a thin shell or shaped xe2x80x9cmembranexe2x80x9d which is stabilized or forced against formable material by a backing liquid. The technique requires a separate forming or fabrication step to create the formed shell or membrane.
U.S. Pat. No. 5,928,597 (Van Ert et al.) is titled xe2x80x9cMethod for Thermoforming Sheet Articlesxe2x80x9d and discloses a method of thermoforming shapes from sheet materials which also utilizes thin shells which are forced against the sheet by a pressurized liquid which also cools the sheet. Again, as with McCollum, the technique requires that specific-use shells be formed as the mold faces. In addition it is not clear that there is a mechanism other than the stiffness of the thin formed shells to prevent distortion of the molded shape by the generally non-uniform resistance of a sheet undergoing thermoforming.
U.S. Pat. No. 3,962,395 (Hxc3xa4gglund) is titled xe2x80x9cMethod of Producing Castings or Other Mouldings by Means of Vacuum Suction of Flexible Containers Holding Granular Material.xe2x80x9d The technique utilizes granular material poured into a container to push against a flexible xe2x80x9cwallxe2x80x9d of the container comprising an elastic sheet or formed plastic film, which in turn is forced against a shape such as the stump of an amputee""s limb. Air is then evacuated or partially evacuated xe2x80x9cto cause the granules to form a solid, persistent mass conforming to the shape of the modelxe2x80x9d which is then removed from contact with the stabilized surface. Hxc3xa4gglund, while interested in a certain degree of accurate conformity to the model, is not concerned, as are Fischer and Uzaki, with a high degree of consolidation of the particulate material without voids.
U.S. Pat. No. 4,327,046 (Davis et al.) is titled xe2x80x9cMethod for Producing a Rigid, Shaped Mass Support Systemxe2x80x9d and describes a flexible container (envelope) of elastic film filled with a mixture of rigid particles and a curable adhesive binder material. The envelope is molded to fit a contour such as a particular portion of a person""s body, and then the envelope is xe2x80x9cevacuated to remove volatiles and fix the shape of the contents of the container,xe2x80x9d following which the binder is cured to solidify the mixture. Then xe2x80x9cthe polymeric film can be stripped away, after which an adhesive paint is applied to seal and protect the surface.xe2x80x9d Again as with Hxc3xa4gglund, the object is not to furnish precise, complex-shape conformability, but rather to follow relatively gentle contours. Also the process again requires a vacuum source to stabilize the molded form.
U.S. Pat. No. 3,608,961 (Von Heck) is titled xe2x80x9cVariable Contour Cushionxe2x80x9d and discloses the application of vacuum to press together and stabilize an air-tight envelope partially filled with bead-like materials. There is no attempt to create a precise fit to complex contours or to minimize the quantity of fluid that is introduced and removed from the envelope.
U.S. Pat. No. 4,885,811 (Hayes) is titled xe2x80x9cProtecting Bodies During Transitxe2x80x9d and shows a restraint consisting of soft, flexible bubbles encased in an air-tight film envelope. The bubbles are soft, having a Shore A Durometer rating of 10 or less. When air is withdrawn from the envelope the restraint molds to the shape of an object which it surrounds, becoming stable while remaining soft and pliable. Again the transfer of air into and out of an envelope is shown, though with the contained bodies being quite resilient when compressed together by ambient pressure. Likewise, there is no attempt to strive for a precise fit to the surrounded body nor to limit quantity of air in and out of the envelope.
U.S. Pat. No. 4,952,190 (Tarnoff et al.) is titled xe2x80x9cDeformable Articlexe2x80x9d and discloses a novelty toy consisting of a flexible shaped bladder with a sealable filling stem which is filled with a moldable filling medium such as a cohesive mixture of hollow or solid microspheres and water. The intent is to product a light, deformable object which can be thrown or caught at significant speed without damaging the objects it hits or a catcher""s hand. There is no intent to control the properties of the mixture beyond furnishing this impact-absorbing deformability.
U.S. Pat. No. 5,093,138 (Drew et al.) shows a flowable, pressure-compensating material which consists of a mixture, composition or medium of spherical bodies in a liquid, though with glycerin or some other additive to increase the viscosity of the composition. It is intended for use in padding devices and is one of several similar media with varying degrees of resistance to flow. There is no provision for varying the flowability or resistance to motion within a single material formulation.
U.S. Pat. No. 5,556,169 (Parrish et al.) is titled xe2x80x9cMulti-Layer Conformable Support Systemxe2x80x9d and describes an outer fluid-sealed layer containing beads which are movable relative to one another when a fluid such as air is introduced, and which are inhibited from motion by atmospheric pressure when the fluid is evacuated. A second fluid-sealed layer underlays the first layer, and air is introduced into it, pushing on the first bead-containing layer and molding it against a shape pressed into the first layer. The technique does not transfer the beads or beadlike structures into and out of the first or any of the layers, which action could achieve the same adjustable conforming effect with a single layer rather than with the multiple coupled layers or compartments shown.
U.S. Pat. No. 5,881,409 (Pearce) is titled xe2x80x9cPuff-Quilted Bladders for Containing Flowable Cushioning Medium.xe2x80x9d The bladders are sealed in a quilted pattern to a base fabric so as to have loose surface skin with many random folds and creases. The cushioning medium is preferred to be lightly lubricated microspheres which the inventor describes in a related U.S. Pat. No. 5,626,657 as being hollow microspheres coated with a lubricant in just sufficient quantity to facilitate sliding and rolling movement between microspheres without physical separation. The desired properties are low specific gravity, low thermal mass, low coefficient of heat transfer, lack of head pressure, insulative and flotation qualities. The system achieves conformability and cushioning through partial fill and limited displacement within the puff-quilted areas.
U.S. Pat. No. 5,966,763 (Thomas et al.) is titled xe2x80x9cSurface Pad System for a Surgical Tablexe2x80x9d and is a more complex version of Parrish""s system due to its application requiring active heating and cooling as well as conforming to portions of a body and restricting movement. The compressible bead-containing xe2x80x9cbagxe2x80x9d has two layers of multiple elements which can be evacuated and there is an underlying inflatable bladder to conform it to a body region prior to stabilizing it. There are also additional layers of heating and cushioning pads.
The present invention provides quickly reversible state-change mixtures which can be rapidly shifted from a near-liquid or fluent state to a stable force-resisting state through slightly altering the liquid-solid proportions, and the invention further provides methods and apparatus for utilizing the mixtures. Embodiments are characterized by one or more of the following advantages: the ability to pressurize a mixture and drive it against a complex surface as if it were a liquid; the ability to create a xe2x80x9cnear-netxe2x80x9d or extremely accurate representation of a shape due to the negligible volumetric change which accompanies a state change; the ability to effect the state-change with a very small volume of single-constituent transfer and with consequently small actuation devices, with a low-energy mechanical actuation, and without requiring a vacuum pump, thermal, chemical or electrical energy to be applied to the mixture; the ability to greatly alter the volume of any elastic or otherwise dimensionally changeable container, envelope or chamber through the free-flowing transfer of the nearly solid mixtures from one container to another; and the ability to tailor the mixtures to satisfy a wide variety of physical specifications in either the flowable or the stable state.
The mixtures can be employed in reformable molds or other shaping tools, and in reusable templates which capture the dimensions of impressed shapes for transfer to a mold. The mixtures can also be used in any product or shape which benefits from the incorporation of arbitrarily reformability or precise reconfigurability. The mixtures further provide useful properties for but are not limited to application in a wide range of shock-absorbing, leveling, protective and supportive apparatus.
In brief, the present invention provides a state-changeable mixture comprising a plurality of solid bodies and a liquid carrier medium of relatively similar density, with the liquid medium filling any voids or interstices between the bodies, preferably excluding air or gas bubbles from the mixture. Within the mixture, the solid bodies can be caused to transition from a formable stage, preferably a near-liquid or fluent condition of mobility, to a stable, force-resisting condition through introduction and then extraction of a slight excess quantity of the carrier medium.
In embodiments, the solid bodies are uniform, generally ordered, and closely-spaced, and to create mobility, the excess amount of liquid (hereinafter called the transition liquid) is introduced in just-sufficient quantity to create a fluent condition by providing a predetermined clearance between the bodies, which clearance permits the gently-forced introduction of at least two simultaneous slip-planes between geometrically ordered bulk masses of the bodies at any point in the mixture.
A surface of the mixture in the formable state, is first made to conform to a desired shape. The bodies in the mixture can then be caused to transition from the fluent condition to the stable condition through extraction of the transition liquid, with the extraction removing the clearance required to provide at least two gently-forced slip-planes between ordered masses of the solid bodies, thereby causing the bodies to make nested, packed, interlocking or otherwise stable consolidated contact. The mixture, in the stable state, now has a surface that conforms to the desired shape.
The invention also provides a method for employing the mixtures in molds, templates or other products of use through holding the mixtures in, or transferring quantities of the mixtures, while in the fluent condition, into and out of variable-contour or variable-volume containers or chambers. The mixtures can be stabilized by removal of the transition liquid, which causes an elastic membrane to be pushed against the consolidated bodies by ambient pressure or which causes the solid bodies to pack together to create an ordered, force-resisting structure through adhesion to one another.
Transfer of fluent mixtures into and out of the containers, or displacement of mixtures within the containers, can be accomplished by pressure forces within the mixture, with these forces being distributed uniformly throughout the mixture by the liquid carrier medium. The pressure forces can be exerted through pressing a shape against an elastic, stretchable membrane which constitutes at least one surface of a chamber substantially filled with the fluent mixture, or the forces within the liquid medium of the fluent mixture can be induced by a reversible fluent-mixture transfer system. There are also various methods of displacing fluent mixtures within variable-volume elastic envelopes by pressing the fluent mixture-filled envelopes against shapes, which pressurizes the carrier medium and causes the envelopes to extend and conform to the shapes as the contained fluent mixtures flow within the envelopes. As previously described, the mixtures are then stabilized by extraction of the transition liquid, creating force-resisting negatives of the original shapes as defined by outer surfaces of the elastic-membrane envelopes or the consolidated surface of the mixture.
Embodiments include further methods of creating a sculptable state in specific state-change mixtures through placing the mixtures in a quasi-stable condition. the solid bodies are held in contact by extraction of a portion of the transition liquid, yet have sufficient lubricity or low contact friction to be displaced relative to one another by externally imposed forces. The bodies can be displaced into voids created within a mass of the quasi-consolidated mixture, or can be progressively displaced along the surface of the medium from one region of the mass to another.
Another state-change mixture utilizes solid bodies as previously described along with a state-changeable liquid carrier medium. The method of changing the mixture from fluent to stable and back again is, as described above, through transfer of a small amount of excess liquid; however, the mixture can be further solidified by changing the state of the carrier medium from liquid to solid.
In yet another embodiment, a state-change mixture is consolidated within a mold chamber and the liquid carrier or a second liquid component is circulated while held to a pressure below ambient. Through heating and cooling of the circulating liquid, the mold itself can be heated or cooled.
Still another embodiment of the state-change mixture has solid bodies which are hollow and very light, and a carrier medium consisting of a liquid-gas froth of similar density. The froth is destroyed when extracted since the gas within it expands and separates from the liquid component; then the froth is reconstituted from the liquid and and reintroduced into the body mass to recreate a fluent mixture. The liquid component of the froth may be a solvatable (solvent-releasable) adhesive which be dried to hold the consolidated bodies together and then re-dissolved by the frothed carrier medium. Very light bodies can also be surrounded by a denser liquid, with the mixture likewise becoming fluent and then stabilized with transfer of a small quantity of transition liquid; however, the tendency of the bodies to adhere together under contact pressure is preferably countered, or liquid-like transfer of the mixture, especially through small lines or passages, becomes difficult if not impossible.
To reiterate, according to embodiments of the invention, the state-change within the mixtures is effected by the transfer of a small amount of excess carrier medium, the transition liquid, into and out of the mixtures. When the transition liquid is present, preferably in just-sufficient quantity to create the degree of support and clearance which provides for at least two slip-planes, the solid bodies have a degree of mobility similar to that of the liquid medium of the mixture. The slip-plane condition can be generated through very small liquid pressure differential or through externally imposed forces which displace the carrier liquid and the supported bodies along with the liquid. Ordered bulk masses of the bodies can shift relative to other ordered masses at any point within a continuous volume of the mixture, and the location of the slip-planes can fluidly shift under any slight differential force transferred from one body to another. It is preferred to prevent frictional contact between bodies during such force transfer by having the liquid medium of the mixture furnish viscous resistance to contact and a light degree of body-surface lubrication.
Lubricity under high contact forces, as is required for many lubricating mediums, is not necessary within the mixtures since the bodies are in effect free-floating during flow, with any imposed liquid pressure forces being uniformly distributed against the surface of each body. For example a nearly ideal aqueous liquid medium can be formed by dissolving a small quantity of a soluble long-chain polymer such as polyethylene oxide into water. The medium carries solid bodies of a similar density without turbulence and friction-producing contact, allows the bodies to make nonlubricated surface contact when the medium is extracted, and causes the bodies to readily separate when the transition liquid is reintroduced.
When the transition liquid is extracted so that the solid bodies are in a stable configuration with ordered, packed and consolidated contact, the degree of resistance to externally imposed forces depends on such tailorable, engineered physical properties as body shape, body elasticity and compressibility, body surface properties of roughness, smoothness or natural molecular adhesion, residual adhesiveness or lubricity of the liquid medium on the contacting surfaces, surface tension of the medium, and variations of liquid medium or body properties with changes of temperature or pressure; alteration of the resistance properties through replacement of the first liquid with a second liquid medium, rinsing of the bodies and the first medium with a second or sequential liquid mediums, vapors or gaseous fluids; and any other engineered variations in the bodies and first liquid medium, and in other sequential introductions of various fluids into the mixtures or through the consolidated bodies. Any adhesive or clinging contact between the bodies is relieved through polar molecular action of the first liquid medium, or through an intermediary treatment with other liquids or fluids prior to reintroduction of the first liquid medium.
Certain preferred embodiments of the invention provide for holding the mixture inside a container or transporting the mixture into a container with at least one flexible, elastically deformable and stretchable wall; and extracting the transition liquid from the mixture so as to cause body-to-body contact and force-resisting stability through pressure external to the container acting on the confined, ordered, abutting bodies. In some embodiments, properties of flow of the mixture and the resistance to deformation of the abutted bodies are predetermined so as to be a function of the imposed external forces, and so to be subject to variable control which allows intermediate quasi-stable, sculptable or displaceable conditions within or on the surface of the bulk mixture. Finally, the degree of accuracy or irregularity on the surface of a stabilized mass of the mixture is dependent on the relationship between the fineness of the dimensions to be captured, a covering membrane""s thickness and conformability, and the size and degree of regular packing order of a state-change mixture""s solid bodies.
Uniform solid bodies with other than spherical geometries can be usefully employed. For instance, hard flake-like bodies can be employed, in which case the flat faces of the bodies can be pressed against one another to create a force-resisting body mass. The flat faces provide many times the surface area contact of abutting spheres, with accordingly higher friction or adhesion potential. If the flakes consist of a laminate which has one side heavier than the carrier medium and one side lighter, and if the flakes are again closely spaced and in a medium which suppresses turbulence and solid body tumbling, the bodies will tend to be supported in, and be consolidated in, an ordered parallel configuration. In this case, as with the spherical bodies, the transition liquid quantity will be just sufficient to create shear motion of body masses under low displacement forces. Finally, if these or any other bodies are very small compared to the container volume and the contours of a shape which is to be replicated, the mobile solid will assume a near-net shape relative to its container and any impressed shape when the tiny proportion of transition liquid is removed.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.